An adjective qualifies or adds meaning to a noun or pronoun by expressing a quality, e.g. a red flower, a prostrate shrub, a sweet scent, small spores, larger fronds. A Latin adjective must be declined so that its case, gender and number agree with those of the noun being qualified.

A participle is a part of a verb that can have the same function as an adjective, e.g. a climbing plant. It may be either a present participle (indicating something current) or a past participle (indicating something that has happened). In English the present participle is usually indicated by the ending ‘-ing’ (e.g. climbing, narrowing), and the past participle by the ending ‘-ed’ (e.g. rolled, folded). Past participles may have other endings, e.g. torn, seen.

Most descriptive specific epithets are either adjectives or adjectival in form, that is they describe an attribute of the plant. Sometimes we use a noun as an epithet and it is said to be in apposition since it is not necessarily explaining or qualifying the generic name and does not have to agree with it in number or gender. Unless it is indeclinable, however, its case does agree. This is important when it comes to writing diagnoses and both generic name and epithet may have to be in the dative or genitive, e.g. Nymphaea lotus (dative Nymphaeae loto), Asclepias fruticosa (genitive Asclepiadis fruticosae).